Some borehole tools employ available hydrostatic pressure at a desired location to selectively set with a remote signal. Typically, a valve member allows hydrostatic pressure to be communicated with one side of a piston where the opposite side is exposed to a far lower pressure so that the pressure imbalance results in a net force that moves the piston where the movement of the piston results in actuation of the tool directly or indirectly.
FIG. 1 shows such a valve that has a housing 1 that holds a valve member 6 that has seals 7 and 8 on one side of passage 20 and seals 9 and 10 on the other side of passage 20. When valve member 6 moves left to open passage 20 the annulus 24 pressure communicates to an actuating piston 16 to set a borehole tool that is not shown. Valve member 6 is biased to the left by spring 11. Valve member 6 is connected to extension 52 by a connecting rod 53. A segmented retainer 5 has its segments held by a peripheral band that is not shown whose ends are retained to each other with a link that is failed by electric current from line 26 causing heat that leads to the failure of the link. When failure occurs the segments are displaced radially so that they are no longer in position to impede movement to the left by extension 52. The spring 11 is able to push the extension 52 and the valve member 6 to the left bringing seals 9 and 10 past the passage 20 for moving a setting piston 16 to set the borehole tool that is not shown with pressure in annulus 24 or alternatively pressure from a connected hydraulic circuit.
While this design has worked in the past it has potential operability issues in that once the fuse is melted and the segments are free to move they may not move cleanly in a radial direction and out of the way of the moving valve member 6. These segments may cock or jam preventing seals 9 and 10 from travel past passage 20 so that setting piston 16 may never trigger due to inability of hydrostatic pressure in annulus 24 or a connected hydraulic circuit to pass through passage 20. The current design with segments held by a garter spring itself held in position with a link that melts from heat provided by electric current is also expensive to produce apart from the reliability issue discussed above.
Devices that release potential energy to set a tool are illustrated in U.S. Pat. Nos. 9,022,440 and 9,428,977.
The present invention addresses these shortcomings of the prior design by providing a material that changes physical properties from a supporting position against bias on the valve member to a reconfigured position where a physical property has changed such that resistance to movement of a valve member is sufficiently decreased to allow the valve member to move to open the passage to the annulus or to a hydraulic pressure source to move an actuating piston on a borehole tool to actuate the borehole tool directly or indirectly. The change in physical property can be accomplished with electric power delivered on wireline or electric line. These and other features of the present invention may be more readily understood from a review of the description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is to be determined from the appended claims.